It appears that the screenshot below constitutes the complete and total extent of documentation for an entirely new framework, "@arcgis/core":
Actually, its apparent that this forum does not support screenshots, so I can only link you to the available documentation in question here.
The documentation links to a repository with several rudimentary examples, none of which make even an attempt to document the API. I have deduced that the below code block should render a map, with a legend, zoom, and search bar, but unfortunately it doesn't.
<arcgis-map item-id="02b37471d5d84cacbebcccd785460e94">
<arcgis-zoom position="top-left" />
<arcgis-search position="top-right" />
<arcgis-legend position="bottom-left" />
</arcgis-map>
Being a developer, I am of course interested in doing more than copy and paste an example from a lone, disinterested example repository. Even worse, there appears to be a cyclical link in the documentation workflow. The website docs above link to the GitHub repository, which links to the NPM package, which links back to the documentation website. None of these artifacts make any attempt to document the API.
Unfortunately, I have nowhere else to look. Are there any more docs? Are they coming soon? Do people really use the new "@arcgis/core" API?